This application is a U.S. National Phase Application under 35 USC 371 of International Application PCT/JP00/007052 (not published in English) filed Oct. 11, 2000.
The present invention relates to a method and apparatus for irradiating an object with an active energy beam in the case of requiring an inert gas or reactive gas atmosphere in the irradiation treatment within an active energy beam irradiating chamber.
A paint, a printing ink, an adhesive, etc., which are cured by irradiation with an active energy beam such as an electron beam or an ultraviolet light are advantageous over the conventional paint, printing ink, adhesive, etc., which are thermally cured and dried, in that the process speed can be increased, that an environmental problem is not generated because a solvent is not used, and that the energy beam irradiation apparatus can be miniaturized, and, thus, have come to be put to a practical use. In the active energy beam irradiation, the irradiation is carried out in many cases under an inert gas atmosphere, and the irradiation under a reactive gas is also being studied. The irradiation under the inert gas atmosphere will now be described mainly in the following.
Some of the paints, printing inks, adhesives, etc. are subject to a curing inhibition caused by oxygen and fail to be cured unless the irradiation is carried out under an inert gas atmosphere such as a nitrogen gas atmosphere. In such a case, it is necessary to supply an inert gas into the irradiating chamber so as to substitute the inert gas in the irradiating chamber for carrying out the active energy beam irradiation. However, where the object to be irradiated is continuous such as a web, it is impossible to close the object transport inlet and outlet, with the result that the amount of the air entering the irradiating chamber together with the web is increased with increase in the processing speed so as to lower the purity of the inert gas atmosphere within the irradiating chamber. As a result, it is unavoidable to increase the amount of the inert gas used, resulting in a serious problem such as an increase in the running cost.
A measure for overcoming the above-noted problem is proposed in, for example, Japanese Patent Disclosure (Kokai) No. 48-86930. It is proposed that the transport outlet of the irradiating chamber of the object is closed by a nip roll or the like, that an inert gas spurting device and a plurality of partitioned chambers are arranged in the transport inlet, and that a gas discharge pipe is arranged in each of the partitioned chambers so as to prevent the air intrusion. It is taught that the particular technique permits lowering the oxygen concentration within the irradiating chamber to several percent or less.
Another measure is proposed in Japanese Patent Disclosure No. 5-60899. It is proposed that a plurality of nozzles for blowing an inert gas against the surface of the target object to be irradiated and a transport duct covering at least partially the roll for guiding the transport of the target object are arranged along the transport passageway of the target object. It is taught that the particular technique permits increasing the utilization rate of the inert gas for forming an inert gas atmosphere in the irradiating region.
Another measure is proposed in Japanese Patent Disclosure No. 60-90762. It is proposed that an inert gas supply section is arranged within the irradiating chamber having the transport inlet sealed with a cylinder of a printing machine and the transport outlet sealed with a pair of rolls, and that a gas discharge section is arranged in the vicinity of the irradiating chamber. It is taught that the particular technique permits decreasing the amount of the inert gas used and also permits a high speed processing.
A still another measure is proposed in Japanese Patent Disclosure No. 9-138300. It is proposed that a transport roll is arranged in the transport inlet so as to narrow the opening, thereby suppressing the supply of the inert gas. It is also taught that it is possible to prevent the fluttering generated along the flow of the target object that is transported continuously.
In the conventional constructions described above, however, it is necessary supply the inert gas to the inert gas spurting nozzles arranged on one or both sides of the irradiating chamber as well as into the irradiating chamber, leading to an increase in the total amount of the inert gas used.
In the case of arranging a gas discharge pipe, it is necessary to control appropriately the atmosphere within the irradiating chamber. However, it is difficult to have the supply amount of the inert gas and the gas discharge amount balanced. Where the supply amount and the discharge amount are markedly unbalanced, a problem is generated that the amount of the inert gas used is increased. Also, where the inert gas having a high flowing speed is spurted from the inert gas spurting nozzle, a negative pressure is established in the vicinity of the nozzle so as to suck the air from the transport inlet and outlet and from the clearance around the irradiating chamber, giving rise to the problem that the oxygen concentration is not lowered to a desired level. In addition, in the apparatus in which a cover is not mounted to the roll, the inert gas leakage takes place in a large amount.
Further, if the inert gas supply section and the gas discharge section are arranged and, particularly, made integral with a printing machine, or if a partitioned chamber is arranged in front of the irradiating chamber, the entire apparatus is rendered bulky. Naturally, the inner volume of the apparatus is increased, resulting in failure to decrease the amount of the inert gas used. Where the transport inlet is sealed by the cylinder of a printing machine, it is necessary to arrange the printing machine and the active energy beam irradiating apparatus as a set. However, it is practically difficult to add an active energy beam irradiating apparatus to the printing machine arranged in advance.
What should be noted is that, in the conventional active energy beam irradiating method and apparatus, measures are certainly taken to increase the gas flow resistance. However, the conventional apparatus and method are irrelevant to the concept of controlling the amount of the gas passing through the transport inlet and outlet. Where the balance of the gas flow resistance is poor, the amount of the inert gas used for forming the inert gas atmosphere was possibly increased.
It should also be noted that, where the atmosphere within the irradiating chamber is held at a negative pressure, the air is sucked in, for example, from the transport inlet and outlet and from the clearance around the irradiating chamber, resulting in failure to substitute an inert gas within the irradiating chamber. In other words, the oxygen concentration within the irradiating chamber fails to be lowered to a desired level.
An object of the present invention is to provide a method and apparatus for the active energy beam irradiation, which permit substituting a gas effectively within the irradiating chamber in performing the active energy beam irradiation.
Another object is to provide a transport duct used in such an active energy beam irradiation apparatus.
Still another object of the present invention is to provide a method and apparatus for an active energy beam irradiation, which permit stably maintaining the atmosphere within the irradiating chamber.
As a result of an extensive research conducted in an attempt to achieve the above-noted objects, the present inventors have found that, in order to substitute a substituting gas within an irradiating chamber while suppressing the amount of the substituting gas, e.g., for suppressing stably the oxygen concentration within the irradiating chamber to a low level while decreasing the amount of the inert gas used, in a transport system for transporting a target object to be irradiated into an irradiating chamber or in a transport system for substantially continuously transporting the target object into the irradiating chamber, it is effective to introduce a substituting gas, e.g., an inert gas, into the active energy beam irradiating chamber and to make the gas flow resistance at the transport outlet equal to or higher than the gas flow resistance in the transport inlet, and that it is particularly effective to make the gas flow resistance in the transport outlet higher than that in the transport inlet.
It has also been found that, in the apparatus capable of achieving the objects described above, it is effective to use ducts given below as means for generating a flow resistance of an inert gas or a reactive gas in the transport inlet and/or the transport outlet:
1. A transport duct including a transport roll and a roll cover covering at least a part of the transport roll, both arranged on one side of any of the front surface and the back surface of a target object to be irradiated, which passes through the transport duct, and at least one partition wall arranged on the other side.
2. A transport duct including a transport roll and a roll cover covering at least a part of the transport roll, both arranged on one side of any of the front surface and the back surface of a target object to be irradiated, which passes through the transport duct, and a cover shaped to conform with the shape of the transport roll and constructed to cover the target object and the transport roll, which is arranged on the other side.
3. A transport duct including a transport roll and a roll cover covering at least a part of the transport roll, both arranged on one side of any of the front surface and the back surface of a target object to be irradiated, which passes through the transport duct, as well as a nip roll and a roll cover covering the nip roll, which are arranged on the other side.
It has been found that it is possible to effectively control the gas flow resistance and to shield effectively the active energy beam by using at least one of the ducts 1, 2 and 3 given above, while the apparatus is compact. By using the duct of the particular construction, it is possible to maintain the oxygen concentration within the irradiating chamber at a low level, with a high stability while decreasing the amount of the inert gas used, compared with the prior art, and to shield the active energy beam such as an X-ray within its own casing.
The term xe2x80x9cgas flow resistancexe2x80x9d implies the flow resistance against the gas. The gas flow is obstructed with increase in the flow resistance.
The present inventors have conducted additional experiments and found that, where a target object to be irradiated is transported into an irradiating chamber at a certain transport speed, it is effective to set up the pressure within the irradiating chamber higher than the pressure outside the irradiating chamber, i.e., the atmospheric pressure in general, in order to stabilize the atmosphere within the irradiating chamber (e.g., in order to maintain a stable inert gas atmosphere having a low oxygen concentration within the irradiating chamber). In other words, it is effective for the differential pressure between the pressure inside the irradiating chamber and the atmospheric pressure to be a positive pressure. It has also been found that it is effective for the differential pressure to be constant.
The present invention has been achieved on the basis of the findings described above.
According to a first aspect of the present invention, there is provided a method for an active energy beam irradiation, the method comprising transporting a target object to be irradiated through a transport inlet of an irradiating chamber for performing an active energy beam irradiation into said irradiating chamber, irradiating the object with an active energy beam in an active energy beam irradiating section under an inert gas or a reactive gas atmosphere, and transporting the object out of the irradiating chamber through a transport outlet of the irradiating chamber, wherein the gas flow resistance at each of the transport inlet and the transport outlet is controlled to meet the condition of X/Yxe2x89xa71, where X represents the amount of the gas passing through the transport inlet, and Y represents the amount of the gas passing through the transport outlet, and the active energy beam irradiation is carried out under the state meeting the condition of X/Yxe2x89xa71.
According to a second aspect of the present invention, there is provided an apparatus for an active energy beam irradiation, comprising an irradiating chamber for irradiating a target object with an active energy beam, said irradiating chamber including a transport inlet for transporting said target object into said irradiating chamber and a transport outlet for transporting said target object out of the irradiating chamber; an irradiating apparatus for irradiating said target object with an active energy beam within said irradiating chamber; and a gas supply mechanism for supplying an inert gas or a reactive gas into said irradiating chamber thereby to set up an inert gas atmosphere or a reactive gas atmosphere within the irradiating chamber, wherein said irradiating chamber includes an irradiating section for irradiating the target object with the active energy beam emitted from said irradiating apparatus and a transport duct having a gas flow resistor serving to set up the condition of X/Yxe2x89xa71, where X represents the gas amount passing through said transport inlet and Y represents the gas amount passing through said transport outlet.
According to the constructions defined in the present invention, it is possible to replace the air within the irradiating chamber by decreasing the amount of the substituting gas used, compared with the prior art. In the case of supplying an inert gas, it is possible to maintain the oxygen concentration within the irradiating chamber at a low level with a high stability while decreasing the amount of the inert gas used, compared with the prior art.
Particularly, where the active energy beam irradiation is carried out under the condition of X/Y greater than 1, the air within the irradiating chamber can be replaced with a smaller amount of the substituting gas used even where the transport speed of the target object is high.
According to a third aspect of the present invention, there is provided an apparatus for an active energy beam irradiation, comprising an irradiating chamber including a transport inlet for transporting said target object into said irradiating chamber and a transport outlet for transporting said target object out of the irradiating chamber; an irradiating apparatus for irradiating said target object with an active energy beam within said irradiating chamber; and a gas supply mechanism for supplying an inert gas or a reactive gas into said irradiating chamber thereby to set up an inert gas atmosphere or a reactive gas atmosphere within the irradiating chamber, wherein said irradiating chamber includes an irradiating section for irradiating the target object with the active energy beam emitted from said irradiating apparatus, a transport duct arranged on the side of said transport inlet, and a transport duct arranged on the side of said transport outlet, the gas flow resistance of the transport duct on the side of the transport outlet being equal to or higher than the gas flow resistance of the transport duct on the side of the transport inlet.
The particular construction defined in the third aspect described above permits replacing the air within the irradiating chamber with a smaller amount of the substituting gas used.
According to a fourth aspect of the present invention, there is provided an apparatus for an active energy beam irradiation, comprising an irradiating chamber including a transport inlet for transporting said target object into said irradiating chamber and a transport outlet for transporting said target object out of the irradiating chamber; an irradiating apparatus for irradiating said target object with an active energy beam within said irradiating chamber; and a gas supply mechanism for supplying an inert gas or a reactive gas into said irradiating chamber thereby to set up an inert gas atmosphere or a reactive gas atmosphere within the irradiating chamber, wherein said irradiating chamber includes an irradiating section for irradiating the target object with the active energy beam emitted from said irradiating apparatus, a transport duct arranged on the side of said transport inlet, and a transport duct arranged on the side of said transport outlet, and wherein said transport duct on the side of the transport inlet includes a transport roll and a roll cover covering at least partially said transport roll, both arranged on one side of any of the front surface and the back surface of the target object passing through said transport duct, and includes a gas flow resistor arranged on the other side and having at least one partition wall or a cover arranged to conform with the shape of said transport roll and constructed to cover the target object and the transport roll; said transport duct on the side of the transport outlet includes a transport roll and a roll cover covering at least partially said transport roll, both arranged on one side of any of the front surface and the back surface of the target object passing through said transport duct, and includes a gas flow resistor arranged on the other side and having a nip roll and a nip roll cover covering said nip roll; and the gas flow resistance of the transport duct on the side of the transport outlet is higher than the gas flow resistance of the transport duct on the side of the transport inlet.
According to a fifth aspect of the present invention, there is provided a transport duct for an apparatus for an active energy beam irradiation, comprising a transport roll and a roll cover covering at least partially said transport roll, both arranged on one side of any of the front surface and the back surface of a target object passing through said transport duct, and a gas flow resistor arranged on the other side and having at least one partition wall.
According to a sixth aspect of the present invention, there is provided a transport duct for an apparatus for an active energy beam irradiation, comprising a transport roll and a roll cover covering at least partially said transport roll, both arranged on one side of any of the front surface and the back surface of a target object passing through said transport duct, and a gas flow resistor arranged on the other side and having a cover shaped to conform with the shape of the transport roll and constructed to cover the target object and the transport roll.
The transport duct according to the fifth and sixth aspects of the present invention is free from the contact of the target object with its surrounding structure by fluttering of the target object so as to make it possible to control strictly the gas flow resistance. In addition, it is possible to shield the active energy beam such as an X-ray. It follows that the particular transport duct permits providing a small active energy beam irradiating apparatus.
According to a seventh aspect of the present invention, there is provided a transport duct for an apparatus for an active energy beam irradiation, comprising a transport roll and a roll cover covering at least partially said transport roll, both arranged on one side of any of the front surface and the back surface of a target object passing through said transport duct, and a gas flow resistor arranged on the other side and having a nip roll and a roll cover covering said nip roll.
The transport duct according to the seventh aspect of the present invention permits strictly controlling the gas flow resistance, permits shielding the active energy beam such as an X-ray, and further permits providing a small active energy irradiating apparatus. In this case, it is possible to shield more effectively the active energy beam such as an X-ray by arranging a pair of nip rolls in a position deviated from the line along which the target object is transported within the irradiating chamber thereby obstructing the straight passageway of the active energy beam such as an X-ray.
According to an eighth aspect of the present invention, there is provided a method for an active energy beam irradiation, in which an inert gas or a reactive gas is introduced into an irradiating chamber for irradiating an active energy beam thereby to set up an inert gas atmosphere or a reactive gas atmosphere within the irradiating chamber, a target object to be irradiated is introduced into said irradiating chamber through a transport inlet of the irradiating chamber for irradiation with the active energy beam in an active energy irradiating section of the irradiating chamber and, then, the target object is transported out of the irradiating chamber through a transport outlet, wherein the pressures both inside and outside the irradiating chamber are measured and the supply of the inert gas or the reactive gas into the irradiating chamber is controlled on the basis of the differential pressure between the pressure inside the irradiating chamber and the pressure outside the irradiating chamber.
According to a ninth aspect of the present invention, there is provided a method for an active energy beam irradiation, in which an inert gas or a reactive gas is introduced into an irradiating chamber for irradiating an active energy beam thereby to set up an inert gas atmosphere or a reactive gas atmosphere within the irradiating chamber, a target object to be irradiated is introduced into said irradiating chamber through a transport inlet of the irradiating chamber for irradiation with the active energy beam in an active energy irradiating section of the irradiating chamber and, then, the target object is transported out of the irradiating chamber through a transport outlet, wherein the pressures both inside and outside the irradiating chamber are measured and the size of the opening in the transport inlet and/or the transport outlet is controlled on the basis of the differential pressure between the pressure inside the irradiating chamber and the pressure outside the irradiating chamber.
According to a tenth aspect of the present invention, there is provided an apparatus for an active energy beam irradiation, comprising an irradiating chamber for irradiating a target object with an active energy beam including a transport inlet for transporting said target object into the irradiating chamber and a transport outlet for transporting the target object out of the irradiating chamber; an irradiating apparatus for irradiating the target object with the active energy beam within said irradiating chamber; a transport mechanism for transporting the target object; a gas supply mechanism for supplying an inert gas or a reactive gas into the irradiating chamber; a differential pressure measuring apparatus for measuring the differential pressure between the pressure inside the irradiating chamber and the pressure outside the irradiating chamber; and a control mechanism for controlling at least one of (a) the supply of the inert gas, (b) the size of the opening in the transport inlet and/or the transport outlet, and (c) the transport speed of the target object, on the basis of the differential pressure measured by said differential pressure measuring apparatus.
According to an eleventh aspect of the present invention, there is provided an apparatus for an active energy beam irradiation, comprising an irradiating chamber for irradiating a target object with an active energy beam including a transport inlet for transporting said target object into the irradiating chamber and a transport outlet for transporting the target object out of the irradiating chamber; an irradiating apparatus for irradiating the target object with the active energy beam within said irradiating chamber; a transport mechanism for transporting the target object; a gas supply mechanism for supplying an inert gas or a reactive gas into the irradiating chamber; a differential pressure measuring apparatus for measuring the differential pressure between the pressure inside the irradiating chamber and the pressure outside the irradiating chamber; a supply amount control mechanism for controlling the supply amount of the inert gas or the reactive gas; an opening control mechanism for controlling the size of the opening of the transport inlet and/or the transport outlet; and a speed control mechanism for controlling the transport speed of the target object, wherein at least one of said supply amount control mechanism, the opening control mechanism, and the speed control mechanism is controlled on the basis of the differential pressure measured by said differential pressure measuring apparatus.
The active energy beam irradiating apparatus according to the eighth to eleventh aspects of the present invention permits stably maintaining the atmosphere, e.g., the inert gas atmosphere, within the irradiating chamber, by measuring the differential pressure between the pressure inside the irradiating chamber and the pressure outside the irradiating chamber. What should also be noted is that, since the inert gas atmosphere can be controlled by a simple and cheap fine differential pressure gage in place of the conventional oxygen densitometer, the apparatus cost can be reduced.